Fuel gauge not working

[Ed Janus]

I have a 2005 lly duramax and when I start the truck the fuel gauge goes up a little bit then drops down to a half a tank under empty with the needle facing down . Is this the stepper motor in the dash cluster ?

 

[duramaxdiesel]

Could also be the sending unit itself. I've had two of them go out on both my race truck and Dually. Have you got a scanner?


Nick

 

[Ed Janus]

Yeah I have acces to a scanner what would the steps be to figure it out

 

[DAVe3283]

I don't know if a regular code scanner would do it, but EFI or a data logger will. You want to read the fuel level reported by the ECU. There are (at least) 2 PIDs, one for fuel sender voltage, and one for fuel level in liters.

The liters should match what is in the tank. I don't know the correct voltage range off the top of my head, so you'd have to look that up.